The continuing purpose of this project is to identify animal models applicable to further research into etiology of cancer in humans. Additionally, as cases accumulate, the probability increases that domestic pets with some types of spontaneous cancers can be identified as representing the effects of low-level environmental exposure to carcinogenic agents. The frequency of cancer in these animals would serve as a warning of general environmental hazard to man. The topics of current interest include: 1) environmentally influenced cancer in dogs relative to the level of industrialization in their county of residence; 2) the epidemiologic features of splenic neoplasms, gatro-intestinal cancer, colorectal cancer, and prostatic cancer in dogs; 3) a case-control study of the long-term effects of Promone and Ovaban in dogs; and 4) morbidity among military working dogs compared to that in pet German Shepherds.